1. Field of the Invention
This invention relates to the manufacture of thermocouples, in particular, high quality, small-scale thermocouples.
2. Description of the Prior Art
The prior art discloses several techniques for forming thermocouples. For example, thermocouples have been formed using welding techniques including spot, carbon arc or heliarc welding or other techniques involving heating and mechanical bonding.
There are at several limitations with these techniques. One problem is that wire breakages are common. A recent mechanical solution to this problem is discussed in an article entitled, "Method and Apparatus for Making Fine Wire Thermocouples", J. Phys. E. Sci. Instrum. 21, 52-54 (1988).
A second problem is the presence of impurities by which are created in the thermocouple by the particular process. These impurities detract from the performance and quality of the thermocouple.
A third problem is the difficulty and expense associated with mechanical bonding techniques.
At least one technique has been proposed to reduce the presence of impurities in a thermocouple. That technique uses electron beam welding. However, a high vacuum is required and the process is quite expensive. In addition, the electron beams may cause the thermocouple leads to outgas. Impurities produced during outgassing can then find their way into the thermocouple.
It is an object of this invention to produce a high quality, small-scale thermocouple that is relatively free of impurities.
A further object of this invention is to produce high quality, small-scale thermocouples using a relatively low cost process and materials.